The report counted 42,000 black-shanked douc langurs along with 2,500 yellow-cheeked crested gibbons in Cambodia's Seima Biodiversity Conservation Area, an estimate that represents the largest known populations for both species in the world.

Prior to the recent discovery in the Seima Biodiversity Conservation Area, the largest known populations were believed to be in adjacent Vietnam, where black-shanked douc langurs and yellow-cheeked crested gibbons hover at 600 and 200 respectively.

There are several large mammals of conservation significance in this ecoregion, including the endangered douc langur (Pygathrix nemaeus), red-cheeked gibbon (Hylobates gabriellae), and pileated gibbon (Hylobates pileatus) and potentially the tiger (Panthera tigris).